Derivatives (Narrative) (Details) (USD $) In Millions	1 Months Ended	6 Months Ended
	May 31, 2011	Jun. 30, 2011
Number of outstanding interest rate swaps terminated	two
Material amount of ineffectiveness		$ 0
Expected earnings transfer		(3.2)
Period over which gain included in AOCI will be transferred to earnings, months		12
Interest Rate Swaps [Member] | Cash Flow Hedging [Member]
Increase in interest expenses	1.5
Expense capitalized	1.1